Conductive element structure and method

ABSTRACT

Conductive element structures and methods of manufacture thereof are disclosed. In some embodiments, a method of forming a conductive element in an insulating layer includes: forming a recess in a metal layer disposed over the insulating layer; selectively forming a metal liner on a sidewall of the recess; and etching a via in the insulating layer using the metal layer and the metal liner as a mask.

BACKGROUND

As consumer devices have gotten smaller and smaller in response toconsumer demand, the individual components of these devices havedecreased in size as well. Semiconductor devices, which make up a majorcomponent of devices such as mobile phones, computer tablets, and thelike, have been pressured to become smaller and smaller, with acorresponding pressure on the individual devices (e.g., transistors,resistors, capacitors, etc.) within the semiconductor devices to also bereduced in size.

One enabling technology that is used in the manufacturing processes ofsemiconductor devices is the use of photolithographic materials. Suchmaterials are applied to a surface and then exposed to an energy thathas itself been patterned. Such an exposure modifies the chemical andphysical properties of the exposed regions of the photolithographicmaterial.

However, as the size of individual devices has decreased, processwindows for photolithographic processing have become tighter andtighter. As such, methods that can keep up the ability to scale down thedevices and meet the desired design criteria are needed such that themarch towards smaller and smaller components may be maintained.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It isnoted that, in accordance with the standard practice in the industry,various features are not drawn to scale. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion.

FIG. 1 shows a method of forming a conductive element in an insulatinglayer, in accordance with some embodiments.

FIG. 2A to FIG. 2F and FIG. 3A to FIG. 3F show process flowsillustrating the method shown in FIG. 1, in accordance with someembodiments.

FIG. 4 and FIG. 5 show methods of forming a conductive element in aninsulating layer, in accordance with some embodiments.

FIG. 6A to FIG. 6N show some of the process steps of the methods shownin FIG. 4 and FIG. 5.

FIG. 7 shows a plurality of conductive element structures formed in aplurality of insulating layers, in accordance with some embodiments.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, orexamples, for implementing different features of the provided subjectmatter. Specific examples of components and arrangements are describedbelow to simplify the present disclosure. These are, of course, merelyexamples and are not intended to be limiting. For example, the formationof a first feature over or on a second feature in the description thatfollows may include embodiments in which the first and second featuresare formed in direct contact, and may also include embodiments in whichadditional features may be formed between the first and second features,such that the first and second features may not be in direct contact. Inaddition, the present disclosure may repeat reference numerals and/orletters in the various examples. This repetition is for the purpose ofsimplicity and clarity and does not in itself dictate a relationshipbetween the various embodiments and/or configurations discussed.

Further, spatially relative terms, such as “beneath,” “below,” “lower,”“above,” “upper” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. The spatiallyrelative terms are intended to encompass different orientations of thedevice in use or operation in addition to the orientation depicted inthe figures. The apparatus may be otherwise oriented (rotated 90 degreesor at other orientations) and the spatially relative descriptors usedherein may likewise be interpreted accordingly.

FIG. 1 shows a method 100 of forming a conductive element in aninsulating layer, in accordance with one or more embodiments. The method100 may include forming a recess in a metal layer disposed over aninsulating layer (in 102); selectively forming a metal liner on asidewall of the recess (in 104); and etching a via in the insulatinglayer using the metal layer and the metal liner as a mask (in 106). Themethod 100 further includes forming a conductive element in the via (in108).

FIG. 2A to FIG. 2F show a process flow illustrating the method 100 shownin FIG. 1, in accordance with one or more embodiments. The process flowin FIG. 2A to FIG. 2F may, for example, be identified with a singledamascene process and may show some of the process steps inmanufacturing a semiconductor device.

As shown in FIG. 2A, a workpiece 200 may be provided. The workpiece 200may include a semiconductor substrate layer 202, an insulating layer204, an etch stop layer 206, and a metal layer 208. The semiconductorsubstrate layer 202 may include, or may be, a semiconductor substrate.The semiconductor substrate may include, or may be, a silicon substrate.Alternatively, the semiconductor substrate layer 202 may include, or mayconsist of, another elementary semiconductor material (such asgermanium); a compound semiconductor material (including siliconcarbide, gallium arsenic, gallium phosphide, indium phosphide, indiumarsenide, and/or indium antimonide); an alloy semiconductor material(including SiGe, GaAsP, AlInAs, AlGaAs, GaInAs, GaInP, and/or GaInAsP);or combinations thereof.

In an embodiment, the semiconductor substrate layer 202 may include, ormay be, a semiconductor on insulator (SOI) substrate. The SOI substratemay include a buried oxide (BOX) layer formed by a process such asseparation by implanted oxygen (SIMOX), and/or other suitable processes.Further, the semiconductor substrate layer 202 may include an epitaxiallayer (epi-layer) that may, for example, be strained for performanceenhancement. The semiconductor substrate layer 202 may include at leastone circuit element (not shown in FIG. 2A) that may be formed in or onthe semiconductor substrate layer 202. For example, the at least onecircuit element may include, or may be, at least one of a transistor, aresistor, a capacitor, and an inductor, although other circuit elementsmay be possible as well.

The insulating layer 204 may be disposed over the semiconductorsubstrate layer 202 (e.g. over a top surface 202 a of the semiconductorsubstrate layer 202). The insulating layer 204 may be formed by chemicalvapor deposition (CVD), physical vapor deposition (PVD), atomic layerdeposition (ALD), a spin-on-dielectric process, combinations thereof, orthe like. The insulating layer 204 may include, or may consist of, adielectric material and may be an interlayer dielectric (ILD) layer. Theinsulating layer 204 may include one or more layers (e.g. one or moreILD layers). In other words, the insulating layer 204 may include, ormay be, a single layer structure (e.g. including one layer of insulatingmaterial) or a multilayer structure (e.g. including two or more layersof insulating material). The insulating layer 204 may include, or mayconsist of, at least one of silicon dioxide, fluorinated silicon glass(FSG), SILK (a product of Dow Chemical of Michigan), BLACK DIAMOND (aproduct of Applied Materials of Santa Clara, Calif.), although otherinsulating materials may be possible as well.

The etch stop layer 206 may be disposed over the insulating layer 204,and the metal layer 208 may be disposed over the etch stop layer 206, asshown in the example of FIG. 2A. The etch stop layer 206 may preventetching of the underlying insulating layer 204 during an etch processthat may be applied to the metal layer 208. The etch stop layer 206 maybe formed over the insulating layer 204 by a deposition process, e.g.CVD, PVD, spin coating, combinations thereof, or the like.

In an embodiment, the etch stop layer 206 may include, or may consistof, TiN or TiO. In another embodiment, the etch stop layer 206 mayinclude, or may consist of, suitable metallic compounds like TaN, NiSi,CoSi, combinations thereof, or the like. The etch stop layer 206 mayhave a thickness in a range from about 150 Å to about 400 Å, althoughother thicknesses may be possible as well.

The metal layer 208 on the etch stop layer 206 may function as a metalhard mask during an etch process that may be applied to the underlyinginsulating layer 204 and etch stop layer 206. The metal layer 208 may beformed over the etch stop layer 206 by an electro-chemical platingprocess, CVD, ALD, PVD, combinations thereof, or the like. The metallayer 208 may include a conductive material. For example, the metallayer 208 may include, or may consist of, at least one of aluminum,cobalt, titanium, and copper, although other metals or metal alloys maybe possible as well. For example, in an embodiment, the metal layer 208may include, or may consist of, suitable metallic compounds like TiN,TaN, NiSi, CoSi, or the like. A thickness T₁ of the metal layer 208 maybe in a range from about 100 Å to about 500 Å, although otherthicknesses may be possible as well.

As shown in FIG. 2B, a first recess 210 may be formed in the metal layer208 by means of an etch process 203. In forming the first recess 210, apatterned etch mask (not illustrated in FIG. 2B) may first be formedover a portion of a top surface 208 a of the metal layer 208. Thepatterned etch mask may be formed by coating a masking material (e.g. aphotoresist) over the top surface 208 a of the metal layer 208, andpatterning the masking material to form the patterned etch mask.Patterning the masking material may include, or may consist of, alithographic process (e.g. a photo-lithographic process). Thereafter,the etch process 203 may be applied in cooperation with the patternedetch mask to form the first recess 210. The etch process 203 may applieduntil a portion of a surface of the etch stop layer 206 is exposed. Theetch stop layer 206 may prevent etching of the underlying insulatinglayer 204 during application of the etch process 203. The patterned etchmask may be removed after forming the first recess 210.

In an embodiment in which the metal layer 208 includes, or consists of,aluminum, the etch process 203 may be a reactive ion etch and mayinclude an etch process chemistry including, or consisting of, achlorine containing etchant, such as Cl_(x) (e.g. Cl₂), although otheretch process chemistries may be possible as well in accordance withother embodiments. The etch process 203 may include a flow rate (e.g. anetchant flow rate) in a range from about 10 standard cubic centimetersper minute (sccm) to about 200 sccm, and may be performed at a pressurein a range from about 100 mT to about 500 mT. The etch process 203 mayinclude provision of electrical power in a range from about 10 Watts toabout 500 Watts.

The first recess 210 may be disposed at the top surface 208 a of themetal layer 208. For example, a mouth of the first recess 210 may bedisposed at the top surface 208 a of the metal layer 208 and may extendinto the metal layer 208. The first recess 210 may include at least onesidewall 210 a and a bottom surface 210 b. A depth D of the first recess210 may, for example, be measured from the mouth of the first recess 210to the bottom surface 210 b of the first recess 210. The depth D of thefirst recess 210 may be substantially equal to the thickness T₁ of themetal layer 208. As in the example shown in FIG. 2B, the at least onesidewall 210 a of the first recess 210 may be substantially straight. Inother words, the at least one sidewall 210 a of the first recess 210 maybe substantially perpendicular to the bottom surface 210 b of the firstrecess 210.

The first recess 210 may have a first width W₁ that may, for example, bemeasured as the widest lateral extent of the first recess 210. Forexample, the first width W₁ may be measured as the distance betweenopposite sidewalls of the first recess 210, as shown in FIG. 2B. Thefirst width W₁ may be in the range from about 20 nm to about 60 nm (e.g.about 40 nm), although other values may be possible as well. The firstwidth W₁ may be the smallest attainable lateral extent of the firstrecess 210 using the patterning process described above with respect toFIG. 2B. In other words, the first width W₁ may be the criticaldimension of the first recess 210 for the patterning process.

As shown in FIG. 2C, a metal liner 212 may be selectively formed on theat least one sidewall 210 a of the first recess 210 by a selectiveprocess 205. In other words, the metal liner 212 may be formed on theconductive material of the metal layer 208, but not on the bottomsurface 210 b of the first recess 210. Stated in yet another way, themetal liner 212 may only be formed over surfaces of the metal layer 208.The metal liner 212 on the at least one sidewall 210 a of the firstrecess 210 may be substantially straight. In other words, the metalliner 212 on the at least one sidewall 210 a of the first recess 210 maybe substantially perpendicular to the bottom surface 210 b of the firstrecess 210, as shown in the example of FIG. 2C. The metal liner 212functions as a self-aligned metal spacer during an etch process that maybe applied to the underlying insulating layer 204 and etch stop layer206.

A thickness T₂ of the metal liner 212 may be measured in a lateraldirection, e.g. from the at least one sidewall 210 a of the first recess210. The thickness T₂ of the metal liner 212 may be in a range fromabout 50 Angstroms to about 150 Angstroms, although other thicknessesmay be possible as well. Accordingly, selectively forming the metalliner 212 on the surfaces of the metal layer 208 may shrink the firstwidth W₁ by about 10 nm (50 Å×2 sidewalls) to about 30 nm (150 Å×2sidewalls). Stated differently, by selectively forming the metal liner212 over the surfaces of the metal layer 208, the first width W₁ may bereduced to a second width W₂, which may be in a range from about 5 nm toabout 20 nm, e.g. in a range from about 5 nm to about 15 nm. A width(e.g. a lateral extent) of a feature (e.g. a via) that may be formed inthe insulating layer 204 may depend at least in part on the second widthW₂. The metal liner 212 may include, or may consist of, at least one ofaluminum, cobalt, titanium, ruthenium, and copper, although other metalsor metal alloys may be possible as well.

In an embodiment, the selective process 205 may include, or may be, aselective plating process or a selective CVD process. In anotherembodiment, the selective process may include, or may be, a selectivedeposition and oxidization process. The selective process 205 forms themetal liner 212 on the conductive material of the metal layer 208, butnot on the surface of the etch stop layer 206 exposed by the firstrecess 210. Such a selective formation of the metal liner 212 on themetal layer 208 may be due to a difference in the composition of themetal layer 208 and the etch stop layer 206. In particular, theconductive material of the metal layer 208 may be able to provide achemical potential (e.g. a redox potential) that is different from theetch stop layer 206 and that is sufficient to cause a chemical reaction(e.g. a reduction) to occur thereon, thus forming the material of themetal liner 212. Consequently, material of the metal liner 212 may beselectively formed on the conductive material of the metal layer 208.

In an embodiment in which the metal liner 212 includes, or consists of,aluminum and in which the selective process 205 is a selective platingprocess, the selective process 205 may includeAlCl₃-1-ethyl-3-methylimidaolium in solution having a concentration in arange from about 20 mole percent to about 40 mole percent along withAlCl₃ in solution having a concentration in a range from about 50 molepercent to about 70 mole percent. The selective process 205 may furtherinclude applying a voltage in a range from about −0.1 V to about −0.2 Vto the metal layer 208 and/or passing a current having a current densityin a range from about 1.5 mA/cm² to about 2.0 mA/cm² through the metallayer 208. The selective process 205 may be performed at a temperaturein a range from about 20 degrees Celsius to about 40 degrees Celsius andat a pressure in a range from about 800 Pa to about 1000 Pa.

In an embodiment in which the metal liner 212 includes, or consists of,copper and in which the selective process 205 is a selective platingprocess, the selective process 205 may include CuSO₄ and NaSO₄ insolution. The selective process 205 may further include applying avoltage in a range from about −0.1 V to about −1 V to the metal layer208 and/or passing a current having a current density in a range fromabout 1.0 mA/cm² to about 5.0 mA/cm² through the metal layer 208. Theselective process 205 may be performed at a temperature in a range fromabout 10 degrees Celsius to about 40 degrees Celsius and at a pressurein a range from about 50 kPa to about 150 kPa.

In an embodiment in which the selective process 205 is a selectivedeposition and oxidization process, a metal or metal alloy may bedeposited on the surfaces of the metal layer 208 and subsequentlyoxidized by an oxidization process. In an embodiment, the oxidizationprocess may include an anodic metal oxidization process. In a particularembodiment, the metal liner 212 may consist of Al₂O₃. In this particularexample, aluminum may be selectively deposited (e.g. by a platingprocess) on surfaces of the metal layer 208 exposed to the selectiveprocess 205. In other words, the exposed surfaces of the metal layer 208may be capped with aluminum by utilizing a difference in chemicalpotential (e.g. redox potential) between the metal layer 208 and theetch stop layer 206.

Once the aluminum has been formed, anodic metal oxidization of thedeposited aluminum may be done by exposing the aluminum to oxalic acidin solution having a concentration in a range from about 0.2 molarity toabout 0.4 molarity, e.g. about 0.3 molarity. The anodic metaloxidization process may further include applying a voltage in a rangefrom about 30 V to about 50 V to the metal layer 208, and may beperformed at a temperature in a range from about 10 degrees Celsius toabout 20 degrees Celsius. In so doing, the metal liner 212 consisting ofAl₂O₃ is formed on the surfaces of the metal layer 208. The anodic metaloxidization process may also result in the surfaces of the metal liner212 being terminated after combining with oxygen.

In another particular embodiment, the metal liner 212 may consist ofCuO₂. The selective process 205 may include deposition of copper on thesurfaces of the metal layer 208, e.g. by a selective plating process. Inother words, the exposed surfaces of the metal layer 208 may be cappedwith copper by utilizing a difference in chemical potential (e.g. redoxpotential) between the metal layer 208 and the etch stop layer 206.

Once the copper has been formed, anodic metal oxidization of thedeposited copper may be done by exposing the copper to NaCl and NaOH insolution having a concentration in a range from about 0.1 molarity toabout 0.5 molarity (e.g. about 0.3 molarity). The anodic metaloxidization process may further include applying a voltage in a rangefrom about 30 V to about 50 V to the metal layer 208, and may beperformed at a temperature in a range from about 50 degrees Celsius toabout 90 degrees Celsius. In so doing, the metal liner 212 consisting ofCuO₂ is formed on the surfaces of the metal layer 208. The anodic metaloxidization process may also result in the surfaces of the metal liner212 being after combining with oxygen.

As shown in FIG. 2D, a via 214 may be etched in the insulating layer 204by means of an etch process 207, using the metal layer 208 and the metalliner 212 as a mask. In other words, a pattern formed by the metal layer208 and the metal liner 212 may be transferred to the insulating layer204. Stated in yet another way, the first recess 210 having the secondwidth W₂ may be extended into the insulating layer 204 to form the via214 in the insulating layer 204. The via 214 in the insulating layer 204may expose a portion of the top surface 202 a of the semiconductorsubstrate layer 202.

The via 214 formed in the insulating layer 204 may have a third width W₃that may be substantially equal to the second width W₂. Accordingly, byshrinking the first width W₁ to the second width W₂, and by extendingthe first recess 210 having the second width W₂ into the insulatinglayer 204, a critical dimension of the via 214 for the process flowshown in FIG. 2A to FIG. 2D may be smaller than the critical dimensionof a via formed by a lithographic process. The critical dimension of thevia 214 for the process flow shown in FIG. 2A to FIG. 2D depends atleast in part on the thickness T₂ of the metal liner 212. Accordingly,the critical dimension of the via 214 for the process flow shown in FIG.2A to FIG. 2D may be controlled by adjusting the thickness T₂ of themetal liner 212, which may, in turn, be varied by controlling the amountof material that is selectively formed on the metal layer 208 during theselective process 205. This may, for example, be controlled by varyingthe process parameters of the selective process 205, e.g.,concentrations of solutions, voltage, current density, temperature,pressure, and duration of the selective process 205.

The etch process 207 may include, or may be, a dry etch processincluding one or more chemical reagents. For example, the etch process207 may include at least one first chemical reagent for etching throughthe etch stop layer 206. The etch process 207 may further include atleast one second chemical reagent for etching through the insulatinglayer 204.

In a particular embodiment in which the etch stop layer 206 includes, orconsists of, TiN or TiO, the at least one first chemical reagent of theetch process 207 may include, or may be, a gaseous etchant containingfluorine, such as C_(x)F_(y) or F_(z). A flow rate of the at least onefirst chemical reagent may be in a range from about 10 standard cubiccentimeters per minute (sccm) to about 200 sccm, and may be at pressurein a range from about 100 mT to about 500 mT. The etch process 207 mayinclude provision of electrical power in a range from about 10 Watts toabout 500 Watts for etching through the etch stop layer 206.

The second chemical reagent of the etch process 207 (for etching throughthe insulating layer 204) may include, or may be, a gaseous etchantcontaining at least one of fluorine and hydrogen, such as H₂,C_(x)F_(y), C_(x)H_(y)F_(z) or F_(x). A pressure of the at least onesecond chemical reagent may be in a range from about 100 mT to about 500mT. The etch process 207 may include provision of electrical power in arange from about 10 Watts to about 2000 Watts for etching through theinsulating layer 204.

As shown in FIG. 2E, the metal liner 212, the metal layer 208, and theetch stop layer 206 may be removed by one or more stripping processes209 to expose a top surface 204 a of the insulating layer 204. The oneor more stripping processes 209 may include one or more chemicalreagents to strip the metal liner 212, the metal layer 208, and the etchstop layer 206, e.g. in sequence. The one or more chemical reagents maybe chosen such that the insulating layer 204 is substantiallyunperturbed. In other words, material of the metal liner 212, the metallayer 208, and the etch stop layer 206 may be removed while maintainingthe integrity of the insulating layer 204.

For example, in an embodiment in which the metal liner 212 and the metallayer 208 includes, or consists of, aluminum, the one or more chemicalreagents of the one or more stripping processes 209 may includephosphoric acid. The phosphoric acid may remove the aluminum containedin the metal liner 212 and the metal layer 208. A temperature of the oneor more stripping processes 209 including phosphoric acid may be in arange from about 24 degrees Celsius to about 45 degrees Celsius.

In another embodiment in which the metal liner 212 and the metal layer208 includes, or consists of, copper, the one or more chemical reagentsof the one or more stripping processes 209 may include at least one ofFeCl₃ and HCl. The FeCl₃ and/or HCl may remove the copper contained inthe metal liner 212 and the metal layer 208. A temperature of the one ormore stripping processes 209 including FeCl₃ and/or HCl may be in arange from about 20 degrees Celsius to about 60 degrees Celsius. The oneor more chemical reagents of the one or more stripping processes 209 mayinclude hydrogen peroxide. The hydrogen peroxide may remove the etchstop layer 206.

As shown in FIG. 2F, a conductive element 216 may be formed in the via214. In other words, the via 214 may be filled with a conductivematerial. The conductive material of the conductive element 216 mayinclude, or may consist of, copper, tungsten, titanium, tantalum,chromium, platinum, silver, gold, combinations thereof, or the like.Additionally, the conductive material may include one or more barriermaterial layers that may line the via 214. The one or more barriermaterial layers, which may include, or may consist of, suitable metalliccompounds like TiN, TaN, NiSi, CoSi, combinations thereof, or the like.

Filling the via 214 with the conductive material may include firstdepositing a seed layer (not shown in FIG. 2F) and electrochemicallyplating the via 214 with the conductive material. The conductivematerial may overfill the via 214, e.g. such that the conductivematerial overlies the top surface 204 a of the insulating layer 204. Achemical mechanical polish (CMP) may be performed to remove excessportions of the conductive material over the insulating layer 204, e.g.such that a top surface 216 a of the conductive element 216 issubstantially co-planar with the top surface 204 a of the insulatinglayer 204.

As seen in the process flow in FIG. 2A to FIG. 2F, by using the metallayer 208 (which functions as a metal hard mask) and the metal liner 212(which functions as a self-aligned metal spacer), the critical dimensionof features formed in the insulating layer 204 can be reduced withoutthe need for a spacer etch back process or for lithography on a spacer,which are needed in a process flow that has a dielectric hard maskand/or a dielectric spacer. Etch back or lithographic processes canadversely affect a profile (e.g. straightness) of the dielectric hardmask and the dielectric spacer and consequently, the critical dimensionof features formed below the dielectric hard mask and the dielectricspacer. Therefore, by using the metal layer 208 and the metal liner 212in the process flow shown in FIG. 2A to FIG. 2F, the profile (e.g.straightness) of the metal hard mask and metal spacer is preserved, thecritical dimension of features (e.g. the via 214) formed below the metalhard mask and metal spacer is improved, and the process flow can beeasily integrated in a manufacturing process.

FIG. 3A to FIG. 3F show a process flow illustrating the method 100 shownin FIG. 1, in accordance with another embodiment. The process flow shownin FIG. 3A to FIG. 3F may be identified with a dual damascene process,e.g. in which an upper portion of the via 214 (e.g. a portion of the via214 proximate the top surface 204 a of the insulating layer 204) may bewidened to form a trench.

FIG. 3A shows the via 214 that may be etched in the insulating layer 204by the etch process 207, using the metal layer 208 and the metal liner212 as a mask. FIG. 3A may, for example, be identified with FIG. 2D.

As shown in FIG. 3B, the first recess 210 may be widened by an etchprocess 301 to form a widened first recess 302 having a fourth width W₄.The fourth width W₄ may be measured as the distance between oppositesidewalls 302 a of the widened first recess 302. The fourth width W₄ maybe greater than the first width W₁ (see FIG. 2B). For example, thefourth width W₄ may be in a range from about 20 nm to about 60 nm,although other widths may be possible as well.

The etch process 301 may, for example, be similar to the etch process203 described above in respect of FIG. 2B. In particular, in forming thewidened first recess 302, a patterned etch mask (not illustrated in FIG.3B) may first be formed over a portion of a top surface 212 a of themetal liner 212. The patterned etch mask may be formed by coating amasking material (e.g. a photoresist) over the top surface 212 a of themetal liner 212, and patterning the masking material to form thepatterned etch mask. Patterning the masking material may include, or mayconsist of, a lithographic process (e.g. a photo-lithographic process).Thereafter, the etch process 301 may be applied in cooperation with thepatterned etch mask to remove portions of the metal liner 212 and themetal layer 208. The etch process 301 may applied until a portion of asurface of the etch stop layer 206 is exposed. The etch stop layer 206may prevent etching of the underlying insulating layer 204 duringapplication of the etch process 301. The patterned etch mask may beremoved after forming the widened first recess 302.

As shown in FIG. 3C, a first metal spacer 304 may be selectively formedon the sidewalls 302 a of the widened first recess 302 by a selectiveprocess 303. In other words, the first metal spacer 304 may be formed onthe conductive material of the metal layer 208, but not cover the etchstop layer 206. Stated in yet another way, the first metal spacer 304may only be formed over surfaces of the metal layer 208. The selectiveprocess 303 may simultaneously form a conductive layer 304 c over thetop surface 212 a of the metal liner 212.

The first metal spacer 304 on the sidewall 302 a of the widened firstrecess 302 may be substantially straight. In other words, the firstmetal spacer 304 on the sidewall 302 a of the widened first recess 302may be substantially perpendicular to the underlying etch stop layer206, as shown in the example of FIG. 3C. The first metal spacer 304 mayfunction as a self-aligned metal spacer during an etch process that maybe applied at a later process step to widen the upper portion of the via214.

A thickness T₃ of the first metal spacer 304 and the conductive layer304 c may be measured in a lateral direction, e.g. from the sidewall 302a of the widened first recess 302 or from the top surface 212 a of themetal liner 212. The thickness T₃ of the first metal spacer 304 and theconductive layer 304 c may be in a range from about 100 Angstroms toabout 300 Angstroms, although other thicknesses may be possible as well.Accordingly, selectively forming the first metal spacer 304 on thesurfaces of the metal layer 208 may shrink the fourth width W₄ by about20 nm (100 Å×2 sidewalls) to about 60 nm (300 Å×2 sidewalls). Stateddifferently, by selectively forming the first metal spacer 304 over thesurfaces of the metal layer 208, the fourth width W₄ may be reduced to afifth width W₅, which may be in a range from about 5 nm to about 30 nm.A width (e.g. a lateral extent) of a feature (e.g. a trench) that may beformed in the insulating layer 204 may depend at least in part on thefifth width W₅. The first metal spacer 304 may include, or may consistof, similar materials as the metal liner 212.

The selective process 303 may include, or may be, a selective depositionand oxidization process. For example, the selective process 303 mayinclude selectively depositing a metal or metal alloy (e.g. containingaluminum or copper) over the surfaces of the metal layer 208 and themetal liner 212. The deposited metal or metal alloy may subsequently beoxidized (e.g. to form Al₂O₃ or CuO₂). The oxidization process of theselective process 303 may include, or may be, an anodic metaloxidization process. Process parameters and chemical reagents for theselective process 303 may be similar to the process parameters andchemical reagents of the embodiment of selective process 205 (describedabove with respect to FIG. 2C) including the selective deposition andoxidization process.

As shown in FIG. 3D, a trench 306 may be etched in a portion of theinsulating layer 204 by means of an etch process 305, using the metallayer 208 and the first metal spacer 304 as a mask. In other words, apattern formed by the metal layer 208 and the first metal spacer 304 maybe transferred to the insulating layer 204. Stated in yet another way,the widened first recess 302 having the fifth width W₅ may be extendedinto a portion of the insulating layer 204. The trench 306 formed in theinsulating layer 204 may have a sixth width W₆, which may besubstantially equal to the fifth width W₅. The trench 306 may be formedby widening the upper portion of the via 214 (e.g. the portion of thevia 214 proximate the top surface 204 a of the insulating layer 204).

The etch process 305 may include, or may be, a dry etch processincluding one or more chemical reagents. For example, the etch process305 may include at least one first chemical reagent for etching throughthe etch stop layer 206 and may include at least one second chemicalreagent for etching through a portion of the insulating layer 204. Theat least one first and second chemical reagents of the etch process 305may be similar to the at least one first and second chemical reagents ofthe etch process 207. Process parameters of the etch process 305 may besimilar to process parameters of the etch process 207 (described abovewith respect to FIG. 2D).

The sixth width W₆ and the fifth width W₅ depend at least in part on thethickness T₃ of the first metal spacer 304. Accordingly, the sixth widthW₆ and the fifth width W₅ may be controlled by adjusting the thicknessT₃ of the first metal spacer 304, which may, in turn, be varied bycontrolling the amount of material that is selectively formed on thesidewalls 302 a of the widened first recess 302 during the selectiveprocess 303. This may, for example, be controlled by varying the processparameters of the selective process 303, e.g., concentrations ofsolutions, voltage, current density, temperature, pressure, and durationof the selective process 303.

As shown in FIG. 3E, the first metal spacer 304, the metal liner 212,the metal layer 208, and the etch stop layer 206 may be removed by oneor more stripping processes 307 to expose the top surface 204 a of theinsulating layer 204. The one or more stripping processes 307 mayinclude one or more chemical reagents to strip the first metal spacer304, the metal liner 212, the metal layer 208, and the etch stop layer206, e.g. in sequence. The one or more chemical reagents of the one ormore stripping processes 307 may be similar to the one or more chemicalreagents of the one or more stripping processes 209 (described abovewith respect to FIG. 2E). Process parameters of the one or morestripping processes 307 may be similar to process parameters of the oneor more stripping processes 209.

As shown in FIG. 3F, a conductive element 308 may be formed in the via214 and the trench 306. In other words, the via 214 and the trench 306may be filled with a conductive material. The conductive material of theconductive element 308 may be similar to the conductive material of theconductive element 216. The conductive element 308 may include one ormore barrier material layers that may line the via 214 and the trench306. The one or more barrier material layers of the conductive element308 may include, or consist of, similar materials as the one or morebarrier material layers of the conductive element 216.

The process of filling the via 214 and the trench 306 with conductivematerial may include first depositing a seed layer (not shown in FIG.3F) and electrochemically plating the via 214 and the trench 306 withthe conductive material. The conductive material may overfill the via214 and the trench 306, e.g. such that the conductive material overliesthe top surface 204 a of the insulating layer 204. A CMP may beperformed to remove excess portions of the conductive material over theinsulating layer 204, e.g. such that a top surface 308 a of theconductive element 308 is substantially co-planar with the top surface204 a of the insulating layer 204.

As seen in the process flow in FIG. 3A to FIG. 3F, by using the metallayer 208 (which functions as a metal hard mask) and the first metalspacer 304 (which functions as a self-aligned metal spacer), thecritical dimension of features formed in the insulating layer 204 can bereduced without the need for a spacer etch back process or forlithography on a spacer, which are needed in a process flow that has adielectric hard mask and/or a dielectric spacer. Etch back orlithographic processes can adversely affect a profile (e.g.straightness) of the dielectric hard mask and the dielectric spacer andconsequently, the critical dimension of features formed below thedielectric hard mask and the dielectric spacer. Therefore, by using themetal layer 208 and the first metal spacer 304 in the process flow shownin FIG. 3A to FIG. 3F, the profile (e.g. straightness) of the metal hardmask and self-aligned metal spacer is preserved, the critical dimensionof features (e.g. the via 214 along with the trench 306) formed belowthe metal hard mask and self-aligned metal spacer is improved, and theprocess flow can be easily integrated in a manufacturing process.

FIG. 4 shows a method 400 of forming a conductive element in a firstrecess and a second recess, in accordance with some embodiments. Themethod 400 may include providing a metal layer disposed over aninsulating layer, the metal layer including a conductive material andhaving a first recess formed therein (in 402); narrowing the firstrecess to form a narrowed first recess by forming a metal liner on theconductive material but not on a bottom of the first recess (in 404);and extending the narrowed first recess into the insulating layer (in406). The method 400 may further include widening the narrowed firstrecess to form a widened first recess and simultaneously etching asecond recess in the metal layer laterally separated from the widenedfirst recess (in 408); selectively forming a first metal spacer over asidewall of the widened first recess and simultaneously forming a secondmetal spacer over a sidewall of the second recess (in 410); and etchinga portion of the insulating layer using the first metal spacer, thesecond metal spacer, and the metal layer as a mask (in 412).

FIG. 5 shows a method 500 of forming a conductive element in a firstrecess, a second recess, and a third recess, in accordance with someembodiments. The method 500 may include forming a first recess in ametal layer disposed over an insulating layer (in 502); selectivelyforming a metal liner on a sidewall of the first recess (in 504);etching a via in the insulating layer using the metal layer and themetal liner as a mask (in 506); widening the first recess to form awidened first recess and simultaneously etching a second recess in themetal layer laterally separated from the widened first recess (in 508);selectively forming a first metal spacer over a sidewall of the widenedfirst recess and simultaneously forming a second metal spacer over asidewall of the second recess (in 510); etching a third recess in themetal layer, wherein a sidewall of the third recess includes at leastone of the first metal spacer and the second metal spacer (in 512); andetching a portion of the insulating layer disposed below the widenedfirst recess, the second recess, and the third recess using the firstmetal spacer, the second metal spacer, and the metal layer as a mask (in514).

FIG. 6A to FIG. 6N show a process flow illustrating some of the processsteps of the method 400 shown in FIG. 4 and the method 500 shown in FIG.5. FIG. 6A shows the via 214 that may be etched in the insulating layer204 by the etch process 207, using the metal layer 208 and the metalliner 212 as a mask. FIG. 6A may, for example, be identified with FIG.2D and FIG. 3A.

FIG. 6B shows a patterned etch mask 602 formed over a portion of the topsurface 212 a of the metal liner 212. The patterned etch mask 602 mayinclude, or may consist of, a photo-resist material, and may be formedby coating a masking material (e.g. photoresist) over the top surface212 a of the metal liner 212, and patterning the masking material toform the patterned etch mask 602. Patterning the masking material mayinclude, or may consist of, a lithographic process whereby the maskingmaterial is exposed to a patterned energy source (e.g., light) anddeveloped.

FIG. 6C shows that the first recess 210 may be widened by an etchprocess 601 to form the widened first recess 302 having the fourth widthW₄. In this embodiment, a second recess 604 that is laterally separatedfrom the widened first recess 302 is simultaneously etched in the metallayer 208. The second recess 604 may have a seventh width W₇, which maybe measured as the distance between opposite sidewalls of the secondrecess 604. The seventh width W₇ may be substantially equal to the firstwidth W₁ (see FIG. 2B).

The etch process 601 may, for example, be similar to the etch process203. The etch process 601 may be applied in cooperation with thepatterned etch mask 602 to transfer the pattern of the patterned etchmask 602 to the metal layer 208, thus forming the widened first recess302 and the second recess 604. The etch process 601 may be applied untila portion of a surface of the etch stop layer 206 is exposed. The etchstop layer 206 may prevent etching of the underlying insulating layer204 during application of the etch process 601. The patterned etch mask602 may be removed after forming the widened first recess 302 and thesecond recess 604.

As shown in FIG. 6D, the first metal spacer 304 may be selectivelyformed on the sidewalls 302 a of the widened first recess 302 by aselective process 603. Simultaneously, a second metal spacer 606 may beselectively formed on sidewalls 604 a of the second recess 604. In otherwords, the first metal spacer 304 and the second metal spacer 606 may beformed on the conductive material of the metal layer 208 and theconductive material of the metal liner 212, but not cover the etch stoplayer 206. Stated in yet another way, the first metal spacer 304 and thesecond metal spacer 606 may only be formed over surfaces of the metallayer 208 and the metal liner 212. The second metal spacer 606 on thesidewall 604 a of the second recess 604 may be substantially straight.In other words, the second metal spacer 606 on the sidewall 604 a of thesecond recess 604 may be substantially perpendicular to the underlyingetch stop layer 206, as shown in the example of FIG. 6D. The secondmetal spacer 606 may function as a self-aligned metal spacer during anetch process that may be applied to the insulating layer 204.

A thickness T₄ of the second metal spacer 606 may be measured in alateral direction, e.g. from the sidewall 604 a of the second recess604. The thickness T₄ of the second metal spacer 606 may besubstantially equal to the thickness T₃ of the first metal spacer 304.Selectively forming the second metal spacer 606 on the surfaces of themetal layer 208 and the metal liner 212 may shrink the seventh width W₇by about 20 nm (100 Å×2 sidewalls) to about 60 nm (300 Å×2 sidewalls).Stated differently, by selectively forming the second metal spacer 606over the surfaces of the metal layer 208 and the metal liner 212, theseventh width W₇ may be reduced to an eighth width W₈, which may be in arange from about 5 nm to about 30 nm. A width (e.g. a lateral extent) ofa feature (e.g. a via) that may be formed in the insulating layer 204may depend at least in part on the eighth width W₈. The second metalspacer 606 may include, or may consist of, similar materials as thefirst metal spacer 304.

The selective process 603 may include, or may be, a selective depositionand oxidization process. For example, the selective process 603 mayinclude selectively depositing a metal or metal alloy (e.g. containingaluminum or copper) over the surfaces of the metal layer 208 and themetal liner 212. The deposited metal or metal alloy may subsequently beoxidized (e.g. to form Al₂O₃ or CuO₂). The oxidization process of theselective process 603 may include, or may be, an anodic metaloxidization process. Process parameters and chemical reagents for theselective process 603 may be similar to the process parameters andchemical reagents of the selective process 303 (described above withrespect to FIG. 3C).

FIG. 6E shows that a pattern formed by the first metal spacer 304, thesecond metal spacer 606, and the metal layer 208 may be transferred tothe etch stop layer 206 by an etch process 605. In other words, the etchstop layer 206 may be etched by the etch process 605 using the firstmetal spacer 304, the second metal spacer 606, and the metal layer 208as a mask. The etch process 605 may be applied until the top surface 204a of the insulating layer 204 is exposed. The etch process 605 mayinclude at least one chemical reagent for etching through the etch stoplayer 206. The at least one chemical reagent of the etch process 605may, for example, be similar to the at least one first chemical reagentof the etch process 207. Process parameters of the etch process 605 may,for example, be similar to the process parameters for the at least onefirst chemical reagent of the etch process 207.

As shown in FIG. 6F, the via 214, the widened first recess 302 and thesecond recess 604 may be filled with a first resist material 608, whichmay include, or may consist of, a photoresist material. The first resistmaterial 608 may be formed by coating resist material (e.g. photoresistmaterial) within the via 214, the widened first recess 302 and over theconductive layer 304 c and patterning the resist material (e.g. by alithographic process). The first resist material 608 may, for example,protect the first metal spacer 304 and the second metal spacer 606during a subsequent etch process that may remove the conductive layer304 c and the metal liner 212.

FIG. 6G shows the removal of the conductive layer 304 c and the metalliner 212 by an etch process 607 that uses the first resist material 608as a mask. Consequently, the first metal spacer 304 and the second metalspacer 606 are protected during the etch process 607. The etch process607 may be applied until the top surface 208 a of the metal layer isexposed. The first resist material 608 may be removed after theconductive layer 304 c and the metal liner 212 are etched.

The etch process 607 may include an etch process chemistry including, orconsisting of, a gaseous etchant. In an embodiment, the gaseous etchantmay contain a noble gas, such as argon or helium. In another embodiment,the gaseous etchant may contain fluorine, such as F_(x) (e.g. F₂). Inyet another embodiment, the gaseous etchant may contain hydrogen, suchas H₂ or CH_(x). A pressure of the gaseous etchant may be in a rangefrom about 100 mT to about 500 mT. The etch process 607 may includeprovision of electrical power in a range from about 500 Watts to about2000 Watts for etching through the conductive layer 304 c and the metalliner 212.

FIG. 6H shows a second resist material 610 formed within the via 214,the widened first recess 302, the second recess 604 and over a portionof the metal layer 208. The second resist material 610 is formed afterremoving the first resist material 608, e.g. by an ashing process incombination with a wet clean process. The second resist material 610 maydefine a mask for a subsequent etching of the metal layer 208. Thesecond resist material 610, which may include, or may consist of, aphotoresist material, may be formed by coating a resist material (e.g.photoresist material) within the via 214, the widened first recess 302and over the metal layer 208 and patterning the resist material (e.g. bya lithographic process, e.g. a photo-lithographic process).

FIG. 6I shows that a third recess 612 may be formed in the metal layer208 by an etch process 609, using the second resist material 610 as amask. As shown in FIG. 6I, the second resist material 610 may cover aportion of at least one of the first metal spacer 304 and the secondmetal spacer 606. This may be because the etch process 609 maypreferentially etch material of the metal layer 208, while leavingmaterial of the first metal spacer 304 and the second metal spacer 606substantially unperturbed. The etch process 609 may be applied until aportion of a surface of the etch stop layer 206 is exposed. The etchprocess 609 may, for example, be similar to the etch process 203. Thesecond resist material 610 may be removed after forming the third recess612.

A sidewall of the third recess 612 may include at least one of the firstmetal spacer 304 and the second metal spacer 606. For example, in theembodiment shown in FIG. 6I, the third recess 612 on the left has thefirst metal spacer 304 as a sidewall. The third recess 612 on the leftalso has the metal layer 208 as another sidewall. By way of anotherexample, the third recess 612 on the right has the first metal spacer304 as a sidewall and the second metal spacer 606 as another sidewall.

The third recess 612 may have a ninth width W₉, which may be measured asthe widest lateral extent of the third recess 612. For example, theninth width W₉ may be measured as the distance between oppositesidewalls of the third recess 612, as shown in FIG. 6I. While the ninthwidth W₉ may be any suitable size, in a particular embodiment, the ninthwidth W₉ may be substantially equal to the first width W₁.

FIG. 6J shows that a pattern formed by the first metal spacer 304, thesecond metal spacer 606, and the metal layer 208 may be transferred tothe etch stop layer 206 by an etch process 611. In other words, the etchstop layer 206 may be etched by the etch process 611 using the firstmetal spacer 304, the second metal spacer 606, and the metal layer 208as a mask. The etch process 611 may, for example, be a dry etch processand may be similar to the etch process 605.

As shown in FIG. 6K, the metal layer 208, the first metal spacer 304 andthe second metal spacer 606 may be removed by one or more strippingprocesses 613 to expose the etch stop layer 206. The one or morestripping processes 613 may include one or more chemical reagents tostrip the metal layer 208, the first metal spacer 304 and the secondmetal spacer 606 from the underlying etch stop layer 206. The one ormore chemical reagents of the one or more stripping processes 613 may besimilar to the one or more chemical reagents of the one or morestripping processes 209. Process parameters of the one or more strippingprocesses 613 may be similar to process parameters of the one or morestripping processes 209.

As shown in FIG. 6L, a portion of the insulating layer 204 may be etchedby an etch process 615, using the etch stop layer 206 as a mask. Inother words, a pattern formed by the etch stop layer 206 may betransferred to the insulating layer 204. A result of this may be aplurality of trenches 614 that may be formed in the insulating layer204.

The etch process 615 may include, or may be, a dry etch processincluding one or more chemical reagents. The one or more chemicalreagents of the etch process 615 may be similar to the second chemicalreagent of the etch process 207 described above in respect of FIG. 2D.Process parameters of the etch process 615 may be similar to processparameters related to the second chemical reagent of the etch process207.

As shown in FIG. 6M, the etch stop layer 206 may be removed (e.g. by awet strip process including, e.g. hydrogen peroxide). Subsequently, aconductive element 616 may be formed in each trench of the plurality oftrenches 614 and in the via 214, as shown in FIG. 6N. The conductivematerial of the conductive element 616 may be similar to the conductivematerial of the conductive element 216. The process of forming theconductive element 616 may be similar to the process of forming theconductive element 216.

As seen in the process flow in FIG. 6A to FIG. 6N, by using the metallayer 208 (which functions as a metal hard mask) and the first andsecond metal spacers 304 and 606 (which function as self-aligned metalspacers), the critical dimension of features formed in the insulatinglayer 204 can be reduced without the need for a spacer etch back processor for lithography on a spacer, which are needed in a process flow thathas a dielectric hard mask and/or a dielectric spacer. Etch back orlithographic processes can adversely affect a profile (e.g.straightness) of the dielectric hard mask and the dielectric spacer andconsequently, the critical dimension of features formed below thedielectric hard mask and the dielectric spacer. Therefore, by using themetal layer 208 and the first and second metal spacers 304 and 606 inthe process flow shown in FIG. 6A to FIG. 6N, the profiles (e.g.straightness) of the metal hard mask and self-aligned metal spacers arepreserved, the critical dimension of features (e.g. the via 214 alongwith the trenches 614) formed in the insulating layer 204 is improved,and the process flow can be easily integrated in a manufacturingprocess.

The conductive elements 616 shown in FIG. 6N may, for example, be afirst metallization layer. As shown in FIG. 7, a second insulating layer704 may be formed on the conductive elements 616 and the insulatinglayer 204, e.g. by CVD, PVD, spin coating, combinations thereof, or thelike. The second insulating layer 704 may include, or may consist of,similar materials as the insulating layer 204. Thereafter, a secondmetallization layer including one or more second conductive elements 716may be formed in the second insulating layer 704 using at least one ofthe method 100 shown in FIG. 1, the method 400 shown in FIG. 4, and themethod 500 shown in FIG. 5. The second conductive elements 716 mayinclude, or may consist of, similar materials as the conductive elements616. This process of depositing an insulating layer and forming one ormore conductive elements in the insulating layer may continue until adesired number of metallization layers and insulating layers are formed.

According to various embodiments presented herein, a method is provided.The method may include forming a recess in a metal layer disposed overan insulating layer; selectively forming a metal liner on a sidewall ofthe recess; and etching a via in the insulating layer using the metallayer and the metal liner as a mask.

According to various embodiments presented herein, a method is provided.The method may include providing a metal layer disposed over aninsulating layer, the metal layer including a conductive material andhaving a first recess formed therein; narrowing the first recess to forma narrowed first recess by forming a metal liner on the conductivematerial but not on a bottom of the first recess; and extending thenarrowed first recess into the insulating layer.

According to various embodiments presented herein, a method is provided.The method may include forming a first recess in a metal layer disposedover an insulating layer; selectively forming a metal liner on asidewall of the first recess; etching a via in the insulating layerusing the metal layer and the metal liner as a mask; widening the firstrecess to form a widened first recess and simultaneously etching asecond recess in the metal layer laterally separated from the widenedfirst recess; selectively forming a first metal spacer over a sidewallof the widened first recess and simultaneously forming a second metalspacer over a sidewall of the second recess; and etching a portion ofthe insulating layer disposed below the widened first recess and thesecond recess using the first metal spacer, the second metal spacer, andthe metal layer as a mask.

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the presentdisclosure. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions, andalterations herein without departing from the spirit and scope of thepresent disclosure.

What is claimed is:
 1. A method, comprising: forming a recess in a metallayer disposed over an insulating layer; selectively forming a metalliner on a sidewall of the recess; and etching a via in the insulatinglayer using the metal layer and the metal liner as a mask.
 2. The methodof claim 1, wherein the selectively forming the metal liner on thesidewall of the recess comprises selectively plating a metal on thesidewall of the recess.
 3. The method of claim 1, wherein theselectively forming the metal liner on the sidewall of the recesscomprises selectively depositing a metal on the sidewall of the recessand oxidizing the metal.
 4. The method of claim 3, wherein the oxidizingthe metal comprises an anodic metal oxidization process.
 5. The methodof claim 1, further comprising: widening the recess to form a widenedrecess by removing the metal liner on the sidewall of the recess and aportion of the metal layer adjacent to the metal liner; selectivelyforming a metal spacer over a sidewall of the widened recess; andetching the insulating layer adjacent to an upper portion of the viausing the metal spacer and the metal layer as a mask.
 6. The method ofclaim 5, wherein the selectively forming the metal spacer on thesidewall of the widened recess comprises selectively depositing a metalon the sidewall of the widened recess and oxidizing the metal.
 7. Themethod of claim 6, wherein the oxidizing the metal comprises an anodicmetal oxidization process.
 8. The method of claim 1, further comprisingforming a conductive element within the via.
 9. A method, comprising:providing a metal layer disposed over an insulating layer, the metallayer comprising a conductive material and having a first recess formedtherein; narrowing the first recess to form a narrowed first recess byforming a metal liner on the conductive material but not on a bottom ofthe first recess; and extending the narrowed first recess into theinsulating layer.
 10. The method of claim 9, wherein the forming themetal liner comprises selectively plating a metal over a sidewall of thefirst recess but not on the bottom of the first recess.
 11. The methodof claim 9, wherein the forming the metal liner comprises selectivelydepositing a metal over a sidewall of the first recess but not on thebottom of the first recess, and oxidizing the metal.
 12. The method ofclaim 9, wherein the metal liner comprises at least one of aluminum,cobalt, titanium, ruthenium, and copper.
 13. The method of claim 9,wherein the metal layer comprises at least one of aluminum, cobalt,titanium, and copper.
 14. The method of claim 9, wherein a thickness ofthe metal liner is in a range from about 50 Angstroms to about 150Angstroms.
 15. The method of claim 9, further comprising: widening thenarrowed first recess to form a widened first recess and simultaneouslyetching a second recess in the metal layer laterally separated from thewidened first recess; selectively forming a first metal spacer over asidewall of the widened first recess and simultaneously forming a secondmetal spacer over a sidewall of the second recess; and etching a portionof the insulating layer using the first metal spacer, the second metalspacer, and the metal layer as a mask.
 16. The method of claim 15,wherein a thickness of the first metal spacer and a thickness of thesecond metal spacer are in a range from about 100 Angstroms to about 300Angstroms.
 17. A method, comprising: forming a first recess in a metallayer disposed over an insulating layer; selectively forming a metalliner on a sidewall of the first recess; etching a via in the insulatinglayer using the metal layer and the metal liner as a mask; widening thefirst recess to form a widened first recess and simultaneously etching asecond recess in the metal layer laterally separated from the widenedfirst recess; selectively forming a first metal spacer over a sidewallof the widened first recess and simultaneously forming a second metalspacer over a sidewall of the second recess; and etching a portion ofthe insulating layer disposed below the widened first recess and thesecond recess using the first metal spacer, the second metal spacer, andthe metal layer as a mask.
 18. The method of claim 17, wherein theselectively forming the metal liner on the sidewall of the first recesscomprises selectively plating a metal on the sidewall of the firstrecess.
 19. The method of claim 17, wherein the selectively forming thefirst metal spacer and the simultaneously forming the second metalspacer comprises selectively depositing a metal on the sidewall of thewidened first recess and the sidewall of the second recess, andoxidizing the metal.
 20. The method of claim 17, further comprising:etching a third recess in the metal layer, wherein a sidewall of thethird recess comprises at least one of the first metal spacer and thesecond metal spacer, wherein the etching the portion of the insulatinglayer comprises etching a portion of the insulating layer disposed belowthe widened first recess, the second recess, and the third recess usingthe first metal spacer, the second metal spacer, and the metal layer asthe mask.